When the Australian Open rolls around in January, Mike Bryan will have to make a very important decision: will he compete with his twin brother Bob, or with the best doubles player in the world—Jack Sock?

On Friday, Mike won a record-extending 18th Grand Slam doubles title with Sock, defeating Lukasz Kubot and Marcelo Melo, 6-3, 6-1. As the Associated Press put it, "Mike Bryan won his first 16 majors with twin brother Bob, who then was sidelined with a hip injury. So Mike paired with Sock and they won Wimbledon in just their second event together."

Growing up in the same USTA Section as Jack was great for my development as a tennis player, but bad for my trophy case. Most of my trips to tournament finals resulted in a loss to Sock, whose 15-year-old forehand was the best in the country for any junior age group. John McEnroe selected him for the Laver Cup this September stating simply, “Jack is the best doubles player in the world.” And he's right.

But why? Let’s investigate.

It all starts with talent. Sock has some of the quickest hands in the world—the ball moves slower for him. Having quick reflexes is one thing, but you also need the God-given ability to put the ball where you want it. All pros can reflex volley, but Jack controls his reflex volleys as good as anyone. Testing Sock’s hands at net is a bad idea.

Then there's physics. Tennis is a scientific sport, a game of millimeters and degrees, and it's been measured that Sock is the only player in the world who can produce more forehand topspin than Rafael Nadal. The combination of his extreme western grip and racquet-head speed produce the tennis equivalent of a Clayton Kershaw curveball—except that Sock's is traveling at 100+ m.p.h. on occasion. Volleying a ball curving up and down is exponentially more difficult than volleying a ball hit on a straight line. It is almost impossible to hit a clean volley when Sock crushes his forehand.

Strategically, there is no scenario where you would have Sock return from the deuce side. His forehand from the ad court is still one of the world’s best, even after such a rough year in singles. You can only find the Sock backhand with your serve, or by hitting towards an unsafe target deep in his doubles alley. Trying to locate the Sock backhand in doubles is a bad strategy—there is too much court available to focus on such a small window that he can cover so well. Sock is going to hit his forehand whether you like it or not.

Last but not least, Sock's personality makes him a wonderful doubles partner. He is fiercely competitive and never shows fear on a tennis court. He also considers himself something of a comedian. Sock will crack a joke right after blasting an unreturnable forehand—he plays his best when he has some fun. Having an ally only amplifies his sense of humor.

If Mike Bryan doesn’t like Jack joking around he can find a new partner for the Australian Open, but chances are his partner won’t be as good.

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